1. Field of Invention
The present invention relates to an apparatus for applying a torque for vibration reduction in a vehicle parking system and a method for controlling the torque. More particularly, it relates to an apparatus for applying a torque for vibration reduction in a vehicle parking system and a method for controlling the torque to reduce vibration and impact noise of a powertrain generated when a parking state of a vehicle on a slope is released, and reduce the operating force for releasing the parking state.
2. Description of Related Art
In general, when a shift lever is moved from the P (parking) position to the R (reverse) position or to the D (drive) position to start a vehicle parked on a slope, large vibration and impact noise are generated in the vehicle, and a high releasing force is required to move the shift lever.
In a typical parking system with a ratchet structure of a parking gear and a sprag, a force generated by the weight of the vehicle and the gradient of a slope causes a force (i.e., torque) that rotates the parking gear, which generates a large frictional resistance between the sprag and a parking cam, and thus the releasing force required to release the shift lever from the parking position is increased.
During parking, a large force is being applied to a powertrain in the rolling direction by a torque generated by the locking of the drive wheels and, at this time, if the sprag is suddenly disengaged with the parking gear (i.e., if the locking of the parking is released), the powertrain returns to its original position, thus generating vibration, impact, and impact noise.
Referring to FIG. 1, a rotating torque is applied to a parking gear 3 by a force generated by the weight of the vehicle and the gradient of the slope on a road, and this rotating torque (F1) of the parking gear 3 generates a force (F2) for raising a sprag 4. In the parking state, the sprag 4 is being in contact with a parking cam 5 and, at this time, if a shift lever 1 is released from the parking position, the parking cam 5 is pulled backward (F3). As a result, the force (F2) for raising the sprag 4 generates a large frictional resistance between the parking cam 5 and the sprag 4, and thus the releasing force required to release the shift lever 1 from the parking position is increased. Moreover, when the vehicle is parked on a slope, a large rolling movement is generated in the powertrain by the torque applied to the drive wheels as shown in FIG. 2. Accordingly, as the parking lever 1 is released from the parking position, the friction between the sprag 4 and the parking gear 3 is removed and, at this time, the powertrain receiving a large force in the rolling direction is returned to its original position, thus generating large vibration, impact, and impact noise.
However, even when this conventional vehicle parking system is configured to satisfy the target value of the initial releasing force required to release the shift lever 1 from the parking position 1 in the design process, the releasing force is increased as the frequency of use of the shift lever 1 is increased. As a result, a shift cable 7 (connected to an operating lever 8) is stretched by the increase in the releasing force, which may displace the position of the shift lever 1. Moreover, the large impact and vibration generated when the shift lever 1 is released from the parking position reduce the quality of the vehicle.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.